Last night a rattle started coming from the engine bay. It sounded like a loose bolt or washer or something vibrating at only certain rpm ranges. Today I tried to find out what was making the noise but after driving for 15min it got worse. Its definitely not coming from the drivetrain as when stationary and in neutral whenever I rev the engine it makes a really unhealthy clickity clack noise at 3000rpm. At idle the engine is smooth and sounds normal. In VTEC it sounds alright too.

The car has about 27000miles and has never been over revved. Could it be bent valves? Could it be the cylinder 4 failiure? Could it be something to do with the spark plug TSB?

Please help! Any suggestions welcome.

 

Also my check engine light has never been on.

 

Here is a link to the #4 cyl. problem that Barry WY put together. It is an excellent thread that everyone could learn from. I hope this information helps.

https://www.s2ki.com/forums/showthread.php?...p?threadid=8051

Good luck,

 

Before getting paranoid about internal engine problems, check to make sure it's not something as simple as a heat shield rattle or other vibrating external engine component.

Do you have an aftermarket exhaust? Some of them allow resonent frequencies that can exacerbate rattles in the engine bay and dashboard.

Since it sounds easily reproducible, rev the engine while looking around under the hood (being careful not to burn yourself, and watching out for the belt and other moving engine components) and see if you can isoloate where the noise is coming from. A mechanic's stethoscope may be useful in this diagnosis, as might a Honda mechanic's trained ear.

 

Heat shield rattle some times sounds like its coming from inside the engine...and can only make noises at certin rpm......check heatshields first!

 

I do have an aftermarket exhaust.
But it has never rattled before.

My next question is:

If there is something wrong with the engine will the CEL always come on?

 

No, there are two types of codes. The first type is a set code which will turn on the light. The other is a pending code which the car will monitor for another occurence within a time period. The period is normally defined in cycles (i.e. engine on, engine up to temp., engine off). Pending codes will not "set" a CEL lamp illumination. You can use a PGM scan tool or OBD-II explorer software and a laptop to check pending codes.
Two common pending codes are the misfire series, PO400 through PO404, as well as the secondary air pump....forget what code that one is but it will store if you rev up the car a lot(as in when you install that new intake or exhaust).

Utah

 

Rattles in my car will come and go depending on external temperature, engine temperature, whether the A/C is on, etc. It's winter time down there so is the rattle occurring more frequently in colder temperatures? Also, as the miles build on any vehicle, rattles become more likely and pronounced.

It's still a question of diagnosis - I recommend an experienced technician by your side to help figure this one out. There's only so much one can do over the Internet.

 

The other thing I forgot to mention is that there is clang noise on firing the engine up, its quiet at idle makes noise at around 3500rpm and goes quite again above that. Friends who know a bit about cars have suggested the main bearing.

Anyways this week I will take my car to my mechanic who is a honda specialist and was the former service manager at a local honda dealer. He should be able to work it out.

Thanks for your help everyone.

 

Main bearing failiure it is.

Bonus points to whoever got the answer right.

My next question is why did it fail? It could not have been lowb oil because I check my oil level religously. What has to be replaced? I have heard honda does not replace bearings but the whole bottom end. Is this true?

How long can I expect my car to be out of action for?